Also, since the enemy gets stronger as the level progresses, I strongly recommend upgrading mana and arrows exclusively, keeping the enemy back just by arrows. The elemental arrows are very strong so I recommend upgrading arrows quickly.
The revenge wave isn't dependent on time, but castle hp. So you have all the time in the world to get a gigantic wave ready then send it in to destroy the castle so quick that when their revenge wave arrives it's already destroyed. I recommend strongest warriors and when you're low on mana, spam hobbits since they're quick and good in numbers.
What if there were "Jobs" mice could get like "Jumper", which lets you jump higher, "Runner", which makes you run faster, or "Ice Jumper" which lets you WJ ice? + if you like this.
 "Arkandian Crusade"){kind=icon}
 "Epic War 2"){kind=icon}
 "Dark Cut 3"){kind=icon}
 "Transformice"){kind=icon}
 "Globetrotter XL"){kind=icon}
 "endeavor"){kind=icon}
 "Light People on Fire"){kind=icon}
 "Idle 2.: Konquest"){kind=icon}
 "Toxers"){kind=icon}
 "Spear and Katana"){kind=icon}
 "The Torture Game 2"){kind=icon}
 "Look out, Mr Johnson!"){kind=icon}
 "Road of the Dead"){kind=icon}